Syringe shields and methods for using same

ABSTRACT

The present invention relates to syringe loading shields for use with syringes during the drawing of aliquots of radioactive materials from shielded vials containing same. Each syringe loading shield is provided with means for shielding radiation emanating from the mouth of the vial during the material-withdrawal, syringe loading process. In a preferred embodiment, the syringe loading shield comprises a radiation detector for detecting and calibrating the radioactive dosage of the material which is drawn into the syringe barrel. In the preferred embodiment, a substantially tubular shield having a high density viewing window recessed therein is disclosed which is comprised of a plurality of sheaths. A novel hand shield and syringe for use with radioactive materials are also disclosed. sp 
     This is a continuation of application Ser. No. 121,211, filed Feb. 13, 1980 now U.S. Pat. No. 4,307,713.

BACKGROUND OF INVENTION

The present invention relates generally to the field of radiationshielding equipment, and more particularly, to shields for use byradio-pharmacists while withdrawing aliquots of radioactive materialscontained within shielded vials.

It has long been known to shield syringes containing radioactivematerials. Heretofore, such syringes have been shielded be devices whichgenerally surround the syringe barrel, while permitting the needle andneedle hub of the syringe to extend beyond the end of the shield. Meanshave been provided in these shields for holding the syringe more or lesssecurely within the shield. Some syringe shields have incorporated ahigh density glass to facilitate viewing of the syringe markings andcontents. In U.S. Pat. No. 3,820,541 a shield for a hypodermic syringeis disclosed which is lead lined and is provided with a bayonet fittingelement engaging the manually engaged end of the syringe. A coil springcooperates with the bayonet fitting element to prevent wobbling betweenthe barrel of the syringe and the barrel of the shield. The barrel ofthe shield is so configured that a small end of the barrel of thesyringe is unconvered to permit visual inspection of flow to and fromthe syringe.

In U.S. Pat. No. 4,062,353 dated Dec. 13, 1977 a syringe shield isdisclosed which is characterized in the provision of a removable,arcuately shaped bushing positionable in the bore of the shield fordecreasing the effective diameter thereof to suport a syringe barrelagainst a single set screw. The bushing is inserted with the syringebarrel into an oversized bore in the shield permitting passage of theneedle of the syringe with an intact needle cover, thereby maintainingthe sterility of the needle.

While most prior art syringe shields provide good finger and handprotection from the radiation coming from within the syringe, suchshields normally offer little or no protection from the radiation comingfrom the mouth of the vial from which the radioactive material is drawn.Even though most such vials are fitted with vial shields, when thecovers of those shields are removed and the vial inverted for dosagewithdrawal, little or no protection is provided against radiationemanating from the mouth of the dosage vial. Further, since most dosagevials contain multiple dosages of radioactive materials, it may readilybe appreciated that the amount of radiation emanating from a dosage vialis normally many times greater than that emanating from a syringecontaining a single dosage of the subject material. Further, in view ofthe orientation of the dosage vial during withdrawal of the radioactivematerial, the radiation emanating from the dosage vial normally extendsover a much greater area of the hand than that emanating from thesubject syringe.

The high density viewing glass of state of the art syringe shields tendsto be easily broken and/or dislodged from its setting in the syringeshield barrel. These windows normally project from the exterior surfaceof these syringe shields, and thus are particularly prone to breakage,etc. Finally, a thick viewing glass makes observation of the volumetricmarkings on a syringe disposed within the shield difficult to read,particularly against a metallic background which is often the color ofthe oxides of lead or tungsten.

According to state-of-the-art methods, it is desirable to measure andcalibrate the radioactive dosage of an aliquot which has been withdrawnfrom a dosage vial into the syringe, prior to the injection of thatmaterial into a patient. This is normally accomplished by inserting theloaded syringe (without syringe shield) into a dose calibrator whichmeasures the amount of radioactivity contained within the syringe. Sincemost radiopharmacists are acutely aware that their total radiationexposure is as dependent upon the time of exposure as it is upon theintensity of that exposure, most radio-pharmacists prefer to workquickly with radioactive materials. Since state of the art syringeshields, even if used during the withdrawal of material from the dosagevial, must be removed in order to calibrate dosage, manyradio-pharmacists omit the use of any syringe shield, at least untilafter calibration has been completed.

SUMMARY OF THE INVENTION

The present invention provides a novel syringe shield for use with asyringe at least during the loading of that syringe with aliquots ofradioactive materials drawn from the mouth of a dosage vial which isotherwise protected by a conventional vial shield. The present inventionprovides a syringe shield and hand shield, each of which is constructedto shield the user from radiation emanating from the mouth of the dosagevial during the loading of the syringe. In the preferred embodiment, asyringe shield is provided having a substantially tubular body forreceiving at least the barrel portion of the syringe, and a mouth shieldmeans connected to and extending transversely away from that body tosubstantially shield the mouth of the vial at least during the drawingof said aliquots. In the preferred embodiment, the mouth shield is asubstantially annular flange which is sized to cover and overlap atleast that portion of the vial shield which surrounds the mouth of thedosage vial. The tubular body preferably also surrounds the needle huband a portion of the needle.

The present invention also provides a syringe shield which is intendedto eliminate the necessity of removing a loaded syringe from its shieldfor transfer to a separate dosage calibration apparatus. In thepreferred embodiment, a radiation detector is disposed within thetubular body of the syringe shield, which detector is connected to aremote dosage calibrator which is capable of calculating and indicatingthe dosage which has been loaded into the syring.

The preferred embodiment syringe shield further comprises a body havinga plurality of sheaths: a non-toxic exterior sheath, an intermediateshielding sheath, and an interior optically-contrasting sheath whichcontrasts with the volumetric markings of a syringe contained within theshield. This laminar construction enables a high-density viewing windowto be recessed within the body of the shield, to thereby reduce thelikelihood that the window will be broken or dislodged from itsmounting.

In alternate embodiments of the present invention, means are providedfor interconnecting the syringe shield to a modified vial shield, andfor temporarily retaining the syringe within the syringe shield duringthe syringe loading process.

The present invention also provides a novel syringe which is otherwisemade of low density materials, but contains a "barrel" shield which isconnected to the syringe plunger and which shields radiation directedgenerally co-axially along the syringe barrel.

An extremely simple hand shield is also disclosed which comprises a dischaving an aperture therethrough for receiving the barrel of a givensyringe, and which may be used during the syringe loading process toprotect the fingers and hand of the user.

As seen from the above, a primary object of the present invention is theprovision of apparatus which reduces the exposure of a radio-pharmacistto radiation during the loading of syringes with radioactive materialsand/or the calibration of dosages contained within those syringes.

Another object of the present invention is the provision of novelmethods for loading and calibrating syringes containing radioactivematerials.

These and other objects of the present invention will become apparentfrom the following more detailed description.

BRIEF DESCRIPTION

FIG. 1 is a cross-section of the preferred embodiment syringe loadingshield of the present invention shown in its engaged position with amodified vial shield containing a dosage vial, and further showing theretention of a syringe in that shield;

FIG. 2 is a cross-section of the apparatus depicted in FIG. 1 takenalong the lines and arrows 2--2 in FIG. 1;

FIG. 3 is a cross-section of the apparatus shown in FIG. 1 taken alongthe lines and arrows 3--3 in FIG. 1, showing the rotation of the syringebetween free and retained positions;

FIG. 4 is a cross-section of an alternate embodiment syringe loadingshield shown with a syringe retained therein which is being loaded froma multidose vial contained within a conventional multidose vial shield;

FIG. 5 is a cross-section of a preferred embodiment hand shieldillustrating the orientation of a fragmentary portion of the base of asyringe and the tips of two of the user's fingers in their associateduse position.

DETAILED DESCRIPTION OF DRAWINGS

It will be understood that while various examples and embodiments of thepresent invention have been selected for the purpose of illustration inconnection with the following description and figures, theseembodiments, examples and figures are representative and not intended tolimit the scope of the present invention, which is defined in theappended claims.

The preferred embodiment syringe loading shield of the present inventioncomprises a tubular body, a mouth shield extending transversely awayfrom the body for a preselected distance to substantially shield themouth of an associated dosage vial, and a radioactive material detectionmeans disposed within said body for detecting the radioactivity of thealiquot drawn into the barrel of the syringe. Referring now to thedrawings, and particularly FIGS. 1-3, the preferred embodiment syringeshield is shown associated with a modified vial shield, designatedgenerally 10, within which is disposed a multi-dose vial, designatedgenerally 12, containing liquid radioactive material 13 which may bewithdrawn through a conventional vial stopper 14. The vial shield 10comprises shielding walls 16 and 18, a shielding base 20, and an annularshielding collar 22 which defines a vial shield mouth within which themultidose vial stopper 14 is disposed to permit access and penetrationby the syringe needle 50. The vial 12 is held in its illustratedposition within the vial shield 10 in a conventional manner, such as byuse of vial shield spacer (not illustrated).

The multi-dose vial shield 10 illustrated in FIG. 1 has been modified tothe extent that it has been provided with a plurality of pins 24 whichare mounted on the collar 22 and which engage, in a bayonet-type manner,a scatter shield portion of the preferred embodiment syringe loadingshield, as described more fully hereinafter.

The preferred embodiment syringe loading shield is intended for use witha modified disposable syringe designated generally 52. This syringe 52comprises a needle 50, needle hub 54, syringe barrel 56, a plunger,designated generally 58, and a syringe base 60 which extends beyond theouter edges of the syringe barrel 56 to define finger-flange portions60a and 60b. In the preferred embodiment, the plunger, designatedgenerally 58, comprises a thumb flange 62, plunger shaft 64 and piston66.

The preferred syringe loading shield, designated generally 100,comprises a body means for receiving at least the barrel portion of thesyringe 52 so that the barrel of the syringe will be entirely containedwithin the body, as will syringe hub 54 and a portion of needle 50. Thissyringe shield is sized so that its base 103 will interfere with fingerflanges 60a and 60b to prevent the syringe from being over-inserted intothe shield, while establishing a syringe position where needle 50penetrates through stopper 14 of the dosage vial 12 so that aliquots ofmaterial may be withdrawn from the vial. In this preferred embodiment,the body means is a substantially tubular body, designated generally102, which comprises an exterior sheath 104, intermediate sheath 106 andinterior sheath 108. Preferably, the exterior sheath 104 and interiorsheath 108 consist of non-toxic, low density materials, such asaluminum, polytetrafluoroethylene (Teflon®), polypropylene,polyethylene, or other suitable plastic materials. The intermediatesheath, 108, is preferably a shielding material, such as lead, tungstenor copper, which is isolated from the environment by its encapsulationin the aforementioned exterior and interior sheaths.

Disposed at the end of the tubular body 102 which is in proximity withthe dosage vial is a mouth shield means which extends transversely awayfrom the body means for a preselected distance to substantially shieldat least the mouth of the vial during at least the withdrawal ofaliquots of radioactive materials. In the preferred embodiment, thismouth shield means comprises an annular mouth shield flange 202 which issized not only to cover the mouth of the multi-dose vial 12, but also toextend over and to cover the mouth of the vial shield 10 and the vialshield collar 22. In order to insure that lateral scatter which mightotherwise occur from between the collar 22 and mouth shield flange 202is prevented, a lateral scatter shield is provided which extends awayfrom the mouth shield flange 202 to surround at least a portion of thecollar 22 of the vial shield. As seen in FIG. 1, a cylindrical,projecting scatter shield ring 204 is illustrated which is substantiallycoaxial with the tubular body 102 of the syringe loading shield andwhich extends for a preselected distance along the sides of vial shieldcollar 22.

During normal use, it is not anticipated that the syringe loading shield100 and vial shield 10 must be interconnected by the radio-pharmacistduring their use. In fact, experience has indicated that mostradio-pharmacists prefer to simply manually position the vial shield 10and syringe shield 100 as shown in FIG. 1. Some radio-pharmacists may,however, desired to removably connect the syringe loading shield 100 toa given vial shield for purposes of convenience or improved safety. Asshown in FIG. 1, therefore, the scatter shield means may comprise avial-shield interconnection means which removably retains the syringeshield in a preselected position relative to the vial shield. As shownparticularly in FIG. 2, the scatter shield projecting ring 204 may beprovided with one or more bayonet slots 204a which are adapted toreceive and, upon rotation, to engage the aforementioned vial shieldpins 24 to accomplish that retention.

In the preferred embodiment, a portion of 204b the scatter shieldprojecting ring 204 may comprise an extension of the exterior sheath 104of the syringe loading shield. In FIG. 1, this sheath is seen to extendlaterally to define mouth shield covering portion 104A, and to form theaforementioned scatter shield ring portion 204b. This construction ispreferred when the exterior sheath 104 is composed of a matrial, such asaluminum, which possesses suitable strength, rigidity and durability.The scatter shield ring 204a should in every event comprise at least onelayer 204b of high density material, which may comprise an extension ofthe mouth shield material 202.

The surface of the mouth shield 200 which is exposed towards the vialshield 10 should be covered by an annular disc which is non-toxic andwhich, when brought in contact with the collar 22 of the vial shield,will not damage that collar. In the preferred embodiment, this mouthshield cover 210 may also be aluminum, or one of the otheraforementioned plastic materials.

In this preferred embodiment, the finger flanges 60a and 60b not onlydefine the syringe insertion distance by interferring with shield base103, but also, upon rotation of the syringe, cooperate with a retainingmeans for selectively retaining the syringe barrel to at least preventthe axial movement of said barrel during the drawing of aliquots fromthe multi-dose vial 12. This retaining means comprises a locking meansfor receiving one of said finger flanges upon rotation of the syringebase 60. This is accomplished by providing a slot defining memberlocated at the end of the syringe loading shield which is remote fromthe aforementioned mouth shield. In the embodiment illustrated in FIG.1, this slot defining member is a panheaded screw 212 which is shownreceiving and retaining finger flange 60b. This inter-relationship, andthe rotation of syringe base 60, are particularly well illustrated inFIG. 3 of the drawings.

In the embodiment illustrated in FIG. 1, the tubular body 102 defines aviewing aperture extending generally co-axially along the syringebarrel. A high density viewing window 230 is shown recessed in thataperture and is seen to substantially fill that aperture. The inner andthe outer surface of this high density viewing window 230 aresubstantially co-planer with the cylindrical planes defined by therespective exterior and interior surfaces of the exterior sheath 104 andinterior sheath 108. In this manner, the high density viewing window 230neither projects into the central bore of the syringe loading shield,nor outwardly from the exterior of that shield. Accordingly, this windowis not prone to dislodgement or breakage during routine use of thesyringe loading shield. Alternatively, a viewing glass may be selectedhaving a thickness which is approximately equal to the thickness of theexterior and intermediate sheaths 104 and 106, in which case a ledge ofinterior sheath material 108 may extend into the viewing aperture toprovide an annular viewing glass mounting surface.

Dosages of radioactive materials are normally measured throughvolumetric indications on the syringe barrel, such as syringe barrel 56,as well as by detecting the amount of radiation emitted from a loadedsyringe which has been transferred to a dosage calibrator. In thepreferred embodiment, the portion of the interior sheath 108 which isdisposed opposite to the viewing aperture is made of a material whichoptically contrasts with the volumetric markings on the syringe to beused. White polytetrafluoroethylene is a material of choice.Polytetrafluorethylene (Teflon®) is a low density material.Polytetrafluoroethylene is also a material possessing a very low slidingfrictional resistance, thereby readily facilitating the insertion andremoval of a syringe into the bore of a syringe shield lined with thismaterial.

In order to accomplish the dose calibration of radioactive materialsloaded into the barrel 56 of the syringe, the preferred embodimentsyringe loading shield is provided with a radioactive material detectionmeans which is disposed within the body means for detecting theradioactivity of the aliquot drawn into the barrel of the syringe. Inthe preferred embodiment, this radioactive material detection means isconnected to a dosage calibration means for calibrating and indicatingthe dosage of radioactive materials contained within the syringe. Thisradioactive material detection means is preferably disposed adjacent toand coaxially along the syringe barrel 56 in its loading position. Thepreferred detection means comprises a detector designated generally 300which may be located between the interior sheath 108 and the outersheath 104. If necessary, in the vicinity of the radiation detector 300,a portion of the outer sheath 104 may be replaced with a shielding plate302, which may be removable for purposes of assembling and/or servicingthe radiation detector 300.

Radiation detector 300 may comprise any one of a number of suchdetectors known to the art. At the present time, the preferred radiationdetector comprises a radio-fluorescent material which is disposedadjacent to the syringe barrel mounted on a ledge of the interior sheathmaterial 108, which has a detection aperture defined therein. Thisradio-fluorescent material may be encapsulated in an appropriate lowdensity container, if desired, for insertion into the position shown forradiation detector 300. In this instance, the preferred dosagecalibration means comprises a light transmission means for transmittinglight generated by the radio-fluorescent material in the presence of asource of radiation. Remote light quantification means may then be usedfor determining and indicating the dosage of matrial which is containedin the barrel of the syringe, as detected by the radiation detector. InFIG. 1, the means for transmitting informtion from the radiationdetector 300 to such a remote location is diagrammatically illustratedby line 306.

An alternative radiation detector 300 which may be used in accordancewith the present invention is an ionization-chamber radiation detector.In this instance, the output from the radiation detector 300 iselectrical, and the mode of transmission of that information is by awire or wires which are represented diagrammatically by line 306. Afurther alternate embodiment radiation detector is a solid stateradiation detector. Once again, the transmission of information to theremote calibrator and indicator is by wires which are diagrammaticallyillustrated by line 306.

The preferred embodiment syringe loading shield is particularly adaptedfor use with a modified syringe which, in combination with the syringeloading shield, helps to shield the user of the syringe from anysubstantial radiation exposure. This preferred embodiment syringe isillustrated as syringe 52 in FIG. 1, and comprises a low density barrel56, a low density plunger 58 slidingly disposed within said barrel, anda plunger shield means 350 connected to said plunger for shieldingradiation transmitted within said barrel towards the user of saidsyringe. In the preferred embodiment, this plunger shield means isapplied over the end of the plunger which is proximate to the user, thatis, it is applied over the thumb plate 62 of the plunger, as for examplethrough application of an adhesive material therebetween. The plungershield means 350 should have a diameter which is at least as great asthe inner diameter of the syringe barrel 56, and less than the maximumdiameter of the syringe base 60. In its preferred form, the plungershield means 350 is a disc of lead, tungsten, copper or other material,which may be coated or treated to prevent toxic contamination of theuser. The half value layer of this shield may be from 1-5, preferablyabout 3.

In another alternate embodiment of the present invention, the plungershield means may be connected to the plunger 58 at other locations,either along the plunger shaft 64 or as a part of, or encapsulated in,the piston 66. When the plunger shield means is disposed within thebarrel 56 of the syringe, it is necessary to guard against anycontamination of the materials to be drawn into the syringe. For thisreason, it may be preferred to provide a disc or plug of shieldingmaterial which is entirely encapsulated in or enclosed by the syringepiston.

As seen in FIGS. 1-3, a simple, reliable, and well shielded syringeloading shield is disclosed which effectively reduces the likelihoodthat its user may be exposed to unacceptable levels of radiation duringsyringe loading processes.

Referring now to FIG. 4, an alternate embodiment, low-cost syringeloading shield is disclosed which possesses many of the advantages ofthe preferred embodiment syringe loading shield illustrated in FIGS.1-3. For purposes of simplicity, corresponding portions of thisembodiment have been numbered with the same numbers which were used inconnection with the embodiment illustrated in FIGS. 1-3. It will benoted that in this embodiment, the syringe shield body 102 and mouthshield 202 comprise a single layer of shielding material. In thisembodiment, an alternate embodiment slot-defining-member 400 isdisclosed which comprises a U-shaped extension of a portion of thetubular body 102. It should be noted that the tubular body of thesyringe loading shield surrounds the entire length of the barrel 56 ofthe syringe, the hub 54 of the needle, and a portion of the needle 50.The annular mouth shield 202 of the embodiment of FIGS. 1-3 has beenretained to substantially shield the mouth of the vial shield 10,however, for puroses of economy the embodiment of FIG. 4 does notcontain any means for creating a removable connection between theillustrated syringe loading shield and the vial shield. The mouth shield202 nonetheless extends across a portion of the mouth of the multi-dosevial and across the collar 22 of the vial shield to terminate slightlytherebeyond. It is anticipated that the outer diameter of the mouthshield 202 should not be any greater than about the outside diameter ofthe vial shield 10.

The syringe shield illustrated in FIG. 4 may also be modified for useduring the injection of materials into a patient, provided the mouthshield is omitted therefrom and the tubular body is terminated, so thatjust the tip of the needle hub and needle are not surrounded by the body102. In fact, when an optically transparent needle hub is utilized withthis modified shield, it is possible for the individual administratingthe injection to observe the color of material within the transparenthub to insure that the needle is located within a vein of the patent.This is accomplished by observing for the color of blood which is drawnback through the needle into the needle hub 54. Accordingly, analternate embodiment syringe shield is provided which may be used afterdose calibration and during transport and injection of the calibrateddose to the patient. Unlike most prior art syringe shields, thisalternate embodiment does not require any high density viewing glass,such as glass 230, and provides substantial shielding not only aroundthe syringe barrel, but also throughout the syringe hub area.

Referring now to FIG. 5, a further alternate embodiment hand shield isdisclosed which may be used in lieu of the syringe loading shieldshereinbefore described. This hand shield comprises a disc of shieldingmaterial having a syringe aperture 510 defined centrally therein. InFIG. 5, a cross-section of this hand shield, designated generally 500,is illustrated showing that shield in association with a foreshortenedsyringe barrel 56, finger flanges 60a and 60b, plunger shaft 64 andthumb plate 62. The tips of the two fingers, such as index and middlefingers 502 and 504, of the user are shown disposed between adjacentportions of finger flanges 60a and 60b and a contiguous portion of thehand shield 500. As used, the syringe is slipped through the aperture510 of the shield 500 prior to loading. The syringe shield 500 is thenbalanced along the upper surfaces of the fingers of the user so that itis in a substantially horizontal position while the syringe itself is ina substantially vertical position ready for the insertion of its needlethrough the stopper of a multi-dose vial for withdrawal on an aliquot ofmaterial. This material may then be withdrawn, the needle removed fromthe vial, and the hand shield-syringe assembly transferred to a dosecalibrator, whereupon the syringe may be quickly removed from theshield.

The disc 500 may be provided with additional outer layers in order tocounteract the toxicity of the selected shielding material and/or toimprove its appearance or rigidity, as desired. These covering materialsmay be stainless steel, or other materials similar to those disclosedfor the exterior and interior sheaths of the embodiment of FIGS. 1-3.

It is preferred that the central aperture 510 defined in the disc 500 beof a sufficient diameter to easily permit the insertion and withdrawalof the subject syringe. In order to insure free movement of the syringewithin the aperture 510, it is preferred to slightly oversize thisaperture by an amount which may be determined by fitting the syringebarrel into the aperture in its position of use and then testing thedegree of rotation of the barrel axis relative to the plane of the discto see if a proper fit has been obtained. A degree of rotation between 5and 25 degrees of the shield with respect to the axis of the barrel ofthe syringe is suitable, while permissible rotations in the order of 10to 15 degrees are preferred.

The outer periphery of the disc should be of a diameter sufficient toshield at least the user's fingers while disposed on either side of thesyringe barrel, and while supporting the disc in a substantiallyhorizontal position while grasping the syringe. Depending upon the sizeof the user's fingers and hand, a disc having a diameter of between 8and 17 centimeters is acceptable, while preferred diameters rangebetween 11 and 15 centimeters. Excellent results have been obtainedusing a disc having a 13 centimeter diameter. Since syringe barrel sizesvary substantially, in accordance with this embodiment of the presentinvention, a radio-pharmacist may equip his facility with a plurality ofdiscs, each of which has apertures which are sized and, if preferred,coded for use with given syringe barrel sizes. In this manner, aperturesneed not be used which are oversized beyond the tolerances abovedescribed. Regardless of the thickness of the disc selected for use inaccordance with the present invention, it is anticipated that in everyinstance the central aperture should be at least about 0.5 millimeterslarger than the outer diameter of the syringe barrel. If desired, largerapertures may be provided to permit syringes to be accepted with theirneedle covers in place.

As used herein the terms "shielding material", "high density material",and "absorbent material" are intended to refer to materials havinggenerally high atomic numbers (Z), such as lead, copper and tungsten,and more particularly to materials which have in their utilizedthickness, half value layers of at least 3, and preferably 4-6. As usedin the present application, the term "low density materials", isintended to refer to materials having low atomic numbers (Z), which arenot particularly good absorbers of radiation, and, which, in theirutilized thicknesses have half value layer values of less than one.

We claim:
 1. A hand shield for use with a syringe at least during theuse of that syringe for drawing aliquots of radioactive materials from avial, comprising a shielding disc, said disc having an aperturecentrally defined therein for receiving a syringe barrel therethrough,said aperture being slightly oversized with respect to the syringebarrel to permit a rotation of the barrel axis with respect to the planeof the disc of between about 5 and 25 degrees.
 2. The invention of claim1 wherein said disc has a diameter sufficient to shield at least theuser's fingers while disposed on either side of the syringe barrel. 3.The invention of claim 2 wherein the diameter of said disc is between 8and 17 cm.
 4. The invention of claim 3 wherein the diameter of said discis between 11 and 15 cm.
 5. The invention of claim 4 wherein thediameter of said disc is about 13 cm.
 6. The invention of claim 1wherein said aperture is at least about 0.5 mm larger than the outerdiameter of the syringe barrel.
 7. A syringe for use with radioactivematerials; comprising:a. a low-density barrel; b. a low-density plungerslidingly disposed within said barrel, and c. a plunger shield meansconnected to said plunger for shielding radiation transmitted withinsaid barrel towards the user of said syringe, said plunger shield meansbeing applied over the end of said plunger which is proximate to saiduser.
 8. A syringe for use with radioactive materials; comprising:a. alow-density barrel; b. a low-density plunger slidingly disposed withinsaid barrel, and c. a plunger shield means connected to said plunger forshielding radiation transmitted within said barrel towards the user ofsaid syringe, said plunger comprising a piston, and wherein said shieldmeans is encapsulated within said piston.